The effects of impurities on the creep and fracture of AISI type 316 stainless steel

The short term creep properties of low and high carbon AISI type 316 stainless steel with and without 0.1% additions of tin and phosphorus have been investigated using 6 experimental casts. Over a range of stresses at 625 deg C and 700 deg C the different casts exhibit a wide variation in properties and the following general observations have been made: (i) the addition of carbon decreases the minimum creep rate, increases the lifetime and does not affect the ductility; (ii) tin considerably decreases the failure ductilities; (iii) phosphorus causes a large decrease in minimum creep rates, increased lifetimes but retains high ductility. To understand the effects of these compositional changes, extensive microstructural work has been performed using optical, scanning electron and transmission electron microscopy. Auger electron spectroscopy has also been used in an attempt to determine the extent of any grain boundary segregation. (author)